Communication apparatus and protocol processing method

ABSTRACT

A disclosed communication apparatus includes a protocol processing unit configured to send and receive link information on a link in a network having a redundant configuration according to a protocol, to build topology information of the network from the link information, and to set up a path in the network based on the topology information. The protocol processing unit includes a link information advertising unit configured to advertise the link information including, for each of protection types of the link, information used to set up the path, a topology information storing unit configured to store the topology information, and a link information receiving unit configured to receive the link information and to store the received link information in the topology information storing unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2006-349993 filed on Dec.26, 2006, with the Japanese Patent Office, the entire contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to technologies for sending andreceiving network topology information including redundancy informationbetween nodes using a routing protocol for generalized multiprotocollabel switching (GMPLS).

2. Description of the Related Art

A technology called multiprotocol label switching (MPLS), in which IPpackets are routed based on labels, has become widely used. Also, atechnology called generalized multiprotocol label switching (GMPLS) isdrawing attention. In GMPLS, the idea of “labels” used for routing IPpackets in MPLS is generalized and adapted for other networkingtechnologies such as time division multiplexing (TDM) and wavelengthdivision multiplexing (WDM) (i.e. TDM layer and wavelength path layer).

In MPLS and GMPLS, a label switched path (LSP) indicating a path or aroute in a network is set up by referring to a label table. Normally, inMPLS and GMPLS, a source node calculates a route to a destination nodeand sets up an LSP for the calculated route using a signaling protocolsuch as the resource reservation protocol-traffic engineering (RSVP-TE).

Route calculation in MPLS and GMPLS is performed based on networktopology information obtained by nodes using a routing protocol such asthe open shortest path first-traffic engineering (OSPF-TE). OSPF-TE isused for traffic engineering in MPLS and is developed by extending OSPFused for IP networks. Also, extensions to OSPF-TE used for GMPLS aredefined in RFC 4203.

In OSPF-TE, each node advertises link information retained in itself toother nodes by opaque link state advertisement (opaque LSA; RFC 2370 andRFC 3630), and each node creates a topology information database of theentire network based on link information from other nodes. In opaqueLSA, link information is advertised in a format called TLV(type/length/value). There are generally two types of TLVs: the routeraddress TLV and the link TLV. In the present application, the link TLVis mainly discussed. A link TLV may include sub-TLVs (RFC 3630 and RFC4203) (sub-TLVs may also be called sub-frames in the presentapplication). FIG. 1 is a drawing illustrating a format of a TLV (RFC3630). FIG. 2 is a drawing illustrating a TLV including sub-TLVs.

There are 16 types of sub-TLVs: types 1 through 9 for trafficengineering in MPLS (RFC 3630), and types 11 through 16 for GMPLS (RFC4203).

Of the 16 types of sub-TLVs, sub-TLV type 7 (may also be called areservable bandwidth sub-frame) is assigned to “Maximum ReservableBandwidth” and is used to advertise a maximum reservable bandwidth(reservable bandwidth information) of a link to other nodes. Sub-TLVtype 14 (may also be called a protection type sub-frame) is assigned to“Link Protection Type” and is used to advertise the reliability of alink. Sub-TLV type 14 contains one of the values as shown in FIG. 3 (RFC4203).

Meanings of some of the values are described below. Explanations ofother values can also be found in RFC 4202. 0x01Extra Traffic means thatthe link is protecting another link or links. LSPs on a link of thistype will be lost if any of the links it is protecting fails. 0x02Unprotected means that there is no other link protecting this link. LSPson a link of this type will be lost if the link fails. 0x20 Enhancedmeans that there are two or more dedicated disjoint links for protectingthis link. For example, it indicates that a 4-fiber bidirectional lineswitched ring (4-fiber BLSR) is being used to protect this link. Patentdocument 1 discloses a technology for setting up a path according toGMPLS.

[Patent document 1] Japanese Patent Application Publication No.2006-135945

[Non-patent document 1] RFC2370, The OSPF Opaque LSA Option, July 1998

[Non-patent document 2] RFC3630, Traffic Engineering (TE) Extensions toOSPF Version 2, September 2003

[Non-patent document 3] RFC4202, Routing Extensions in Support ofGeneralized Multi-protocol Label Switching (GMPLS), October 2005

[Non-patent document 4] RFC4203, OSPF Extensions in Support ofGeneralized Multi-protocol Label Switching (GMPLS), October 2005

As described above, a sub-TLV for advertising reliability of a link isdefined in OSPF-TE for GMPLS. However, there is one problem in using asynchronous optical network/synchronous digital hierarchy (SONET/SDH)path in a BLSR as a link for setting up an LSP. In the descriptionsbelow, a SONET/SDH path is called a “line” to distinguish it from a path(LSP) set up on a link (TE link).

In a BLSR, a SONET/SDH line may be used as a normal line, a protectionchannel access (PCA) line, or a non-preemptible unprotected traffic(NUT) line. A normal line has a backup line and if the normal linefails, traffic is switched to the backup line. A PCA line is used as abackup line. When an active line being protected by the PCA line fails,the traffic currently flowing through the PCA line is stopped. A NUTline is an active line having no backup line. When the NUT line fails,the traffic flowing through the NUT line is lost.

When using a SONET/SDH line in a BLSR as a link for an LSP, for example,a normal line corresponds to an “Enhanced” link defined by RFC 4202, aPCA line corresponds to an “Extra Traffic” link, and a NUT linecorresponds to an “Unprotected” link.

Multiple SONET/SDH lines can be set up in a link between nodes, and eachof the SONET/SDH lines may be assigned to a normal line, a PCA line, ora NUT line of a BLSR. With the current routing protocol standards forGMPLS, however, it is not possible to advertise the protection typeregarding redundancy for each of the SONET/SDH lines in a link.

FIG. 4 is a drawing illustrating an exemplary network including a BLSR.In the exemplary network shown in FIG. 4, a BLSR is formed by a ringconnecting nodes B, D, D, and E. No backup lines are provided for lines(links) between nodes A and B, nodes A and M, nodes M and Z, and nodes Zand D. Texts provided on the lines between nodes indicate theirbandwidths.

FIG. 5 is a table showing exemplary topology information retained ineach node according to the current OSPF-TE. The exemplary topologyinformation includes only parameters necessary for the descriptionsgiven below.

With the current OSPF-TE, as described above, each node can advertiseonly one protection type and one type of reservable bandwidthinformation for each link. Therefore, as shown in FIG. 5, the exemplarytopology information includes only one protection type and one type ofreservable bandwidth information for each link. For example, theexemplary topology information includes only a protection type“Enhanced” and reservable bandwidth information “12ch” (which indicates12 channels are available) for the link between nodes B and C. In thepresent application, a “channel” indicates the smallest unit ofbandwidth of a SONET/SDH line.

In the network shown in FIG. 4, it is possible to set up an LSP havinghigh reliability by referring to the connection information, theprotection types, and the reservable bandwidth information shown in FIG.5. For example, when setting up an LSP from node A to node Z, an LSPA-B-C-D-Z or A-B-E-D-Z, which goes through the BLSR, may be selectedaccording to the topology information shown in FIG. 5.

However, with the topology information shown in FIG. 5, for example, itis not possible to set up a low-cost LSP using PCA lines since only oneprotection type is provided for each link. Also, although it isnecessary to use the same type of synchronous transport signal (STS)channels of SONET (or the same type of synchronous transport module(STM) channels of SDH) when setting up an LSP on normal lines in a BLSR,it is not possible to advertise STS (or STM) channel information withthe current GMPLS standards. In other words, a node cannot distinguishtypes of STS channels in a link when calculating a route to set up anLSP. Therefore, with the current OSPF-TE or the MPLS/GMPLS standards, itis not possible to select the same type of STS channels for an LSP to beset up on normal lines at the route calculation stage, and it is onlypossible to select the same type of STS channels when setting up the LSPby using a signaling protocol.

The above problem may be solved by defining an original TLV having aproprietary type number and by advertising redundancy information usingthe original TLV. However, if the proprietary type number is assigned toa new TLV type in a standard in the future, the original TLV becomesunusable. If different types of TLVs are assigned to the same typenumber, it causes a malfunction of a network apparatus. Therefore,defining an original TLV is not an appropriate way to solve the problem.

The above problem applies not only to a case where an LSP is set up in anetwork including a BLSR but also to a case where an LSP is set up in anetwork having any type of redundant configuration.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide protocol technologies forsending and receiving network topology information including redundancyinformation that solve or reduce one or more problems caused by thelimitations and disadvantages of the related art.

An embodiment of the present invention provides a communicationapparatus including a protocol processing unit configured to send andreceive link information on a link in a network having a redundantconfiguration according to a protocol, to build topology information ofthe network from the link information, and to set up a path in thenetwork based on the topology information. The protocol processing unitincludes a link information advertising unit configured to advertise thelink information including, for each of protection types of the link,information used to set up the path, a topology information storing unitconfigured to store the topology information, and a link informationreceiving unit configured to receive the link information and to storethe received link information in the topology information storing unit.

Another embodiment of the present invention provides a method of sendingand receiving link information on a link in a network having a redundantconfiguration according to a protocol, where the link information isused to build topology information of the network and the topologyinformation is used to set up a path in the network. The method includesa link information advertising step of advertising the link informationincluding, for each of protection types of the link, information used toset up the path; and a link information receiving step of receiving thelink information and storing the received link information to build thetopology information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing illustrating a format of a TLV;

FIG. 2 is a drawing illustrating a TLV including sub-TLVs;

FIG. 3 shows values specified in a sub-TLV type 14;

FIG. 4 is a drawing illustrating an exemplary network including a BLSR;

FIG. 5 is a table showing exemplary topology information obtained by andretained in each node according to the current OSPF-TE;

FIG. 6 is a block diagram illustrating an exemplary functionalconfiguration of a communication apparatus 10;

FIG. 7 is a table showing a part of exemplary topology informationstored in a topology information database 24 of the communicationapparatus 10;

FIG. 8 is a table showing the remaining part of the exemplary topologyinformation stored in the topology information database 24 of thecommunication apparatus 10;

FIG. 9 is a flowchart showing a first exemplary link information sendingprocess by the communication apparatus 10;

FIG. 10 is a drawing illustrating sub-TLV 9 (1);

FIG. 11 is a drawing illustrating sub-TLV 9 (2);

FIG. 12 is a drawing illustrating sub-TLV 9 (3);

FIG. 13 is a flowchart showing a first exemplary link informationreceiving process by the communication apparatus 10;

FIG. 14 is a flowchart showing a second exemplary link informationsending process by the communication apparatus 10;

FIG. 15 is a drawing illustrating sub-TLV 9 (4); and

FIG. 16 is a flowchart showing a second exemplary link informationreceiving process by the communication apparatus 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described below withreference to the accompanying drawings. The exemplary network shown inFIG. 4 is used in the descriptions below.

FIG. 6 is a block diagram illustrating an exemplary functionalconfiguration of a communication apparatus 10 used as nodes in theexemplary network shown in FIG. 4. The communication apparatus 10includes a protocol processing unit 20 and a primary signal transferunit 30. The protocol processing unit 20 performs protocol processingfor setting up LSPs and includes a control signal sending/receiving unit21, a routing protocol processing unit (link information advertisingunit) 22, a signaling protocol processing unit 23, and a topologyinformation database (topology information storing unit) 24.

The control signal sending/receiving unit 21 sends and receives controlsignals (e.g. IP packets) used in a routing protocol such as OSPF-TE andcontrol signals used in a signaling protocol such as RSVP-TE. Therouting protocol processing unit 22 performs processes related to arouting protocol. For example, the routing protocol processing unit 22advertises and collects topology information, and calculates routes. Therouting protocol processing unit 22 includes a link informationadvertising unit (not shown) that advertises link information, and alink information receiving unit (not shown) that receives advertisedlink information and stores the received link information in thetopology information database 24. The signaling protocol processing unit23 sets up LSPs according to a signaling protocol such as RSVP-TE. Thetopology information database 24 stores network topology informationobtained by the routing protocol processing unit 22. The protocolprocessing unit 10 may be implemented by a hardware circuit or by acomputer including a CPU and a memory and a program for causing thecomputer to perform protocol processing. Protocol processing accordingto embodiments of the present invention is mainly performed by therouting protocol processing unit 22.

The primary signal transfer unit 30 transfers signals through an LSP andincludes a primary signal sending/receiving unit 31, a primary signalswitching unit 32, and a primary signal switching control unit 33. Theprimary signal sending/receiving unit 31 is connected to a link (e.g. anSTS line of SONET or an STM line of SDH; hereafter a link is called anSTS line for descriptive purposes), and sends and receives primarysignals (user data). The primary signal switching unit 32 connects STSlines and switches primary signals. The primary signal switching controlunit 33 controls the primary signal switching unit 32 according tosetting information specified by the signaling protocol processing unit23.

The protocol processing unit 20 and the primary signal transfer unit 30may be provided in the same apparatus or may be provided in separateapparatuses. When the protocol processing unit 20 and the primary signaltransfer unit 30 are provided in the same apparatus, a physicalinterface may be provided for each of them or one physical interface maybe used for both of them. When the protocol processing unit 20 and theprimary signal transfer unit 30 are provided in separate apparatuses, acommunication path for control signal transmission may be provided asidefrom a communication path for primary signals.

FIGS. 7 and 8 are tables showing exemplary topology information of theexemplary network shown in FIG. 4, which topology information is storedin the topology information database 24 of the communication apparatus10. Information items shown in FIGS. 7 and 8 are provided fordescriptive purposes and may not necessarily be consistent with eachother.

As shown in FIGS. 7 and 8, the exemplary topology information includesreservable bandwidth information for each combination of the protectiontypes (Enhanced, Unprotected, and Extra Traffic) and line types (STS1,STS3C, and STS12C) of a BLSR link, and channel availability information.For example, the topology information for the B-C link includes 12ch,STS1-12ch, STS3C-3ch, and STS12C-0ch for the protection type “Enhanced”;STS1-20ch, STS3C-6ch, and STS12C-1ch for the protection type“Unprotected; STS1-4ch, STS3C-1ch, and STS12C-0ch for the protectiontype “Extra traffic”; and a bitmap representing channel availabilityinformation (in the bitmap, 0 indicates that the channel is availableand 1 indicates that the channel is occupied). The topology informationas described above makes it possible, for example, to set up an LSP onPCA lines or an LSP on normal lines using the same type of channels.

In the exemplary topology information shown in FIGS. 7 and 8, reservablebandwidth information is provided line type by line type for each of theprotection types. Alternatively, reservable bandwidth information may beprovided protection type by protection type for each of the line types.For example, in this case, Enhanced-12ch, Unprotected: 20ch, and ExtraTraffic-4ch are provided for the line type STS1 of the link B-C.

In the exemplary topology information, additional information (multipleprotection types and multiple types of reservable bandwidth information)is provided only for links constituting the BLSR. Alternatively,additional information may be provided also for links not constitutingthe BLSR (e.g. A-B, A-M, and so on).

Exemplary processes of generating, sending, and receiving linkinformation by the communication apparatus 10, i.e. each node, aredescribed below. The exemplary topology information as shown in FIGS. 7and 8 is obtained by each node through those processes.

<FIRST EXAMPLE>

FIG. 9 is a flowchart showing a first exemplary link information sendingprocess by the communication apparatus 10. This process is performed bythe routing protocol processing unit 22 of the communication apparatus10.

In step 1, the communication apparatus 10 generates a TLV frame. In step2, the communication apparatus 10 generates a TLV of LSA type 10 (opaqueLSA). In step 3, the communication apparatus 10 generates sub-TLV 1,sub-TLV 2, sub-TLV 3, sub-TLV 4, sub-TLV 5, sub-TLV 6, sub-TLV 7,sub-TLV 8, sub-TLV 9, sub-TLV 11, sub-TLV 14, sub-TLV 15, and sub-TLV16. The number following each sub-TLV indicates the type of the sub-TLV.Steps 1 through 3 conform to the current OSPF-TE. It is not alwaysnecessary to generate all of the sub-TLVs mentioned above. In step 43,sub-TLVs required by the current OSPF-TE (mandatory sub-TLVs) andsub-TLVs necessary for the current process are generated.

In step 4, the communication apparatus 10 generates sub-TLV 9 (1) (thenumber in brackets is used to distinguish different sub-TLVs 9) and setsa fixed bit pattern as the value as shown in FIG. 10. Sub-TLV type 9(administrative group sub-frame) is defined in the OSPF-TE as“Administrative Group”. Sub-TLV 9 (1) tells the receiving node to startprotocol processing of the first example. In step 5, the communicationapparatus 10 generates sub-TLV 9 (2) and sets a value indicatinginformation that follows. For example, the value of sub-TLV 9 (2) is setas shown in FIG. 11.

When bits 0 through 8 of the value are 1 and other bits are 0 (i.e.Value=11111111100000000000000000000000), it indicates that reservablebandwidth information for each combination of the line types STS1,STS3C, and STS12C and the protection types Enhanced, Unprotected, andExtra Traffic is to be sent following sub-TLV 9 (2). A pair of sub-TLVs,sub-TLV 14 and sub-TLV 7, are used to send reservable bandwidthinformation for each of the combinations. Sub-TLV 14 indicates aprotection type and sub-TLV 7 indicates reservable bandwidthinformation. Therefore, the number of pairs of sub-TLVs 14 and 7corresponds to the number of 1 s in bits 0 through 14 of sub-TLV 9 (2).

In step 6, the communication apparatus 10 generates a correspondingnumber of pairs of sub-TLVs 14 and 7 in sequence according to the valueof sub-TLV 9 (2). The type of information contained in each of sub-TLVs14 and 7 is compliant with the current OSPF-TE.

In steps 8 and 9, the communication apparatus 10 generates sub-TLV 9 (1)and sub-TLV 9 (2) again. The value of sub-TLV 9 (2) generated in step 8indicates that channel availability information follows. For example,when bit 26 shown in FIG. 11 is 1, it indicates that channelavailability information for 12 channels (12 bits) is to be sent.

In step 9, the communication apparatus 10 generates sub-TLV 9 (3) andsets channel availability information as the value. As shown in FIG. 12,channel availability information is represented by a bitmap each bit ofwhich corresponds to one channel. For example, if bit 11 of the bitmapis 1, it indicates that the 12th channel is occupied.

In step 10, the communication apparatus 10 again generates sub-TLV 7,sub-TLV 9, and sub-TLV 14, which are the same as those generated in step3. In step 11, the communication apparatus 10 sends the TLV framecontaining the sub-TLVs generated in steps 3 through 10.

The descriptions below explain the reason why a set of sub-TLVsconforming to the current OSPF-TE are generated in step 3 and sub-TLVs7, 9, and 14 conforming to the current OSPF-TE are generated again instep 10.

In the current OSPF-TE, a node does not receive two or more sub-TLVs ofthe same type. Therefore, if a conventional communication apparatusconforming to the current OSPF-TE receives two or more sub-TLVs of thesame type, the apparatus may handle the sub-TLVs in one of the followingmanners (a) and (b):

(a) Trusts the first one of the received sub-TLVs of the same type anddiscards the rest of them.

(b) Trusts the last one of the received sub-TLVs of the same type anddiscards the rest of them; or repeats a process of overwriting apreceding sub-TLV by a succeeding sub-TLV of the same type and therebykeeps the last one of the received sub-TLVs of the same type.

Sending a set of sub-TLVs conforming to the current OSPF-TE in step 3makes it possible for a conventional communication apparatus of type (a)to correctly handle a TLV sent from the communication apparatus 10 ofthis embodiment. Sending sub-TLVs 7, 9, and 14 conforming to the currentOSPF-TE again in step 10 makes it possible for a conventionalcommunication apparatus of type (b) to correctly handle a TLV sent fromthe communication apparatus 10 of this embodiment.

Thus, the exemplary link information sending method shown in FIG. 9 canbe used in a network including both conventional communicationapparatuses not supporting a protocol of this embodiment andcommunication apparatuses supporting the protocol.

FIG. 13 is a flowchart showing a first exemplary link informationreceiving process by the communication apparatus 10.

In step 21, the communication apparatus 10 receives a TLV frame fromanother communication apparatus. Then, in step 22, the communicationapparatus 10 determines whether the LSA type number in the received TLVframe is 10 (opaque LSA). If the LSA type number is not 10 in step 22,i.e., if the received link information is not for GMPLS, thecommunication apparatus 10 discards the received TLV frame in step 23.

If the LSA type number is 10 in step 22, the communication apparatus 10processes the sub-TLVs in the TLV frame in sequence through step 24 andsubsequent steps. In the descriptions below, a sub-TLV currently beingprocessed is called the current sub-TLV.

If the current sub-TLV is not sub-TLV 9 (1) in step 25, i.e., if thetype number of the current sub-TLV is not 9 and/or the value is notidentical with that shown in FIG. 10, the communication apparatus 10performs a corresponding process for the current sub-TLV in step 26. Ifthe current sub-TLV is sub-TLV 9 (1) in step 25, the communicationapparatus 10 determines whether the next sub-TLV is sub-TLV 9 (2) instep 27. In other words, the communication apparatus 10 determineswhether the type number of the next sub-TLV is 9 and the value conformsto the format shown in FIG. 11.

If the next sub-TLV is not sub-TLV 9 (2) in step 27, the communicationapparatus 10 performs a corresponding process for the next sub-TLV instep 26. If the next sub-TLV is sub-TLV 9 (2) in step 27, thecommunication apparatus 10 reads the value of sub-TLV 9 (2), therebydetermines whether subsequent information is reservable bandwidthinformation or channel availability information, and startscorresponding protocol processing in step 28 or 33. Here, “protocolprocessing” indicates a process of analyzing sub-TLVs and obtainingreservable bandwidth information or channel availability information.

Assuming that the TLV frame is generated as described with reference toFIG. 9, sub-TLV 9 (2) indicates that reservable bandwidth informationfor each combination of line types and protection types is contained insubsequent sub-TLVs. Therefore, the communication apparatus 10 proceedsto step 28 and starts the corresponding protocol processing. In thesubsequent step 29, the communication apparatus 10 determines whetherthe type number of the next sub-TLV is 14 (Link Protection Type). If thetype number is not 14, the communication apparatus 10 returns to step24. If the type number is 14 in step 29, the communication apparatus 10determines whether the type number of the next sub-TLV is 7 (MaximumReservable Bandwidth) in step 30. If the type number is not 7, thecommunication apparatus 10 returns to step 24.

If the type number is 7 in step 30, the communication apparatus 10, instep 31, obtains the protection type in sub-TLV 14 and the reservablebandwidth information in sub-TLV 7, and stores them in the topologyinformation database 24 in association with a link corresponding to thereceived TLV frame. For example, when the communication apparatus 10 isnode B shown in FIG. 4 and the received TLV frame contains informationon the link E-D, the protection type and the reservable bandwidthinformation are associated with the link E-D and stored in the topologyinformation database 24.

In step 32, the communication apparatus 10 determines whether all pairsof sub-TLVs 14 and 7 have been processed according to the value ofsub-TLV 9 (2) identified in step 27. If NO in step 32, the communicationapparatus 10 repeats steps 29 through 31 and stores the protection typesand the reservable bandwidth information as described above. If YES instep 32, the communication apparatus 10 returns to step 24.Alternatively, step 32 may be omitted and the communication apparatus 10may be configured to exit the loop of steps 29 through 31 when it cannotfind sub-TLV 14 or sub-TLV 7.

In step 24, the communication apparatus 10 determines whether allsub-TLVs have been processed. If NO in step 24, the communicationapparatus 10 tries to find sub-TLV 9 (1) and sub-TLV 9 (2) in steps 25and 27. Since the TLV frame of this example is generated as shown inFIG. 9, the communication apparatus 10 finds sub-TLV (1) in step 25 andsub-TLV (2) in step 27. The value of sub-TLV (2) found in step 27indicates that channel availability information is to be sent.

The communication apparatus 10 starts protocol processing in step 33 anddetermines whether the next sub-TLV is sub-TLV 9 (3) in step 34. If thenext sub-TLV is not sub-TLV 9 (3), the communication apparatus 10returns to step 24. If the next sub-TLV is sub-TLV 9 (3), thecommunication apparatus 10 obtains the channel availability informationin sub-TLV 9 (3) and stores the information in association with thecorresponding link in the topology information database 24 in step 35.Then, the communication apparatus 10 returns to step 24 and processesthe remaining sub-TLVs.

<SECOND EXAMPLE>

A second exemplary link information sending process and a secondexemplary link information receiving process by the communicationapparatus 10 are described below. FIG. 14 is a flowchart showing asecond exemplary link information sending process by the communicationapparatus 10.

In step 41, the communication apparatus 10 generates a TLV frame. Instep 42, the communication apparatus 10 generates a TLV of LSA type 10(opaque LSA). In step 43, the communication apparatus 10 generatessub-TLV 1, sub-TLV 2, sub-TLV 3, sub-TLV 4, sub-TLV 5, sub-TLV 6,sub-TLV 7, sub-TLV 8, sub-TLV 9, sub-TLV 11, sub-TLV 14, sub-TLV 15, andsub-TLV 16. As in the first example, steps 41 through 43 conform to thecurrent OSPF-TE. It is not always necessary to generate all of thesub-TLVs mentioned above. In step 43, sub-TLVs required by the currentOSPF-TE and necessary for the current process are generated.

In step 44, as in step 4 of the first example, the communicationapparatus 10 generates sub-TLV 9 (1) containing a fixed bit patterntelling the receiving node to start protocol processing. In step 45, thecommunication apparatus 10 generates sub-TLV 9 (4) containing reservablebandwidth information for each combination of line types and protectiontypes and a bitmap representing channel availability information.

FIG. 15 is a drawing illustrating sub-TLV 9 (4). As shown in FIG. 15,sub-TLV 9 (4) contains values 1 through 15 corresponding to reservablebandwidth information for combinations of line types and protectiontypes, and values 16 through 21 corresponding to bitmaps representingchannel availability information.

In step 46, the communication apparatus 10 again generates sub-TLV 9,which is the same as that generated in step 43. Then, in step 47, thecommunication apparatus 10 sends the TLV frame containing the sub-TLVsgenerated in steps 43 through 46.

The reason why a set of sub-TLVs conforming to the current OSPF-TE aregenerated in step 43 and the same sub-TLV 9 is generated again in step46 is substantially the same as explained in the first example.

FIG. 16 is a flowchart showing a second exemplary link informationreceiving process by the communication apparatus 10.

The communication apparatus 10 receives a TLV frame from anothercommunication apparatus in step 51 and determines whether the LSA typenumber in the received TLV frame is 10 (opaque LSA) in step 52. If theLSA type number is not 10 in step 52, i.e., if the received linkinformation is not for GMPLS, the communication apparatus 10 discardsthe received TLV frame in step 53.

If the LSA type number is 10 in step 52, the communication apparatus 10processes the sub-TLVs in the TLV frame in sequence through step 54 andsubsequent steps. In step 55, the communication apparatus 10 determineswhether the current sub-TLV is sub-TLV 9 (1). If the current sub-TLV isnot sub-TLV 9 (1) in step 55, the communication apparatus 10 performs acorresponding process for the current sub-TLV in step 56. If the currentsub-TLV is sub-TLV 9 (1) in step 55, the communication apparatus 10determines whether the next sub-TLV is sub-TLV 9 (4) in step 57. If thenext sub-TLV is not sub-TLV 9 (4), the communication apparatus 10performs a corresponding process for the next sub-TLV in step 56. If thenext sub-TLV is sub-TLV 9 (4), the communication apparatus 10 obtainsthe reservable bandwidth information and the channel availabilityinformation in sub-TLV 9 (4) and stores the information in associationwith the corresponding link in the topology information database 24 instep 58. Then, the communication apparatus 10 returns to step 54 andprocesses the remaining sub-TLVs.

The main difference between the first and second examples is in the useof sub-TLV 9. Sub-TLV 9 is originally designed for various uses and cancontain data of variable length. Using this characteristic of sub-TLV 9,both reservable bandwidth information and channel availabilityinformation are packed into sub-TLV 9 (4) in the second example. On theother hand, in the first example, sub-TLV 9 (2) is used as a markerindicating the information that follows, the protection type and thereservable bandwidth information are sent using sub-TLVs 14 and 7, andthe channel availability information is sent using sub-TLV 9 (3). Thetype of information contained in each of sub-TLVs 14 and 7 is compliantwith the current OSPF-TE. In other words, in the first example, sub-TLVs14 and 7 are used for their original purposes. Also, since sub-TLV 9 (2)is used just as a marker and sub-TLV 9 (3) is used to send only channelavailability information, their sizes are small compared to the size ofsub-TLV 9 (4) used in the second example. With the methods described inthe first and second examples, substantially the same topologyinformation as shown in FIGS. 7 and 8 can be obtained.

An embodiment of the present invention makes it possible to advertiselink information that is used to build topology information of a networkand includes, for each of the protection types of a link, informationused to set up a path. This in turn makes it possible to set up a pathbased on the topology information taking into account the protectiontypes of a link.

An embodiment of the present invention makes it possible to advertisereservable bandwidth information for each combination of protectiontypes and line types of a link, and channel availability informationindicating availability of channels of lines provided by the link.

Embodiments of the present invention make it possible to send andreceive network topology information including redundancy informationand thereby make it possible to flexibly set up a path taking intoaccount line types and protection types.

The present invention is not limited to the specifically disclosedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention.

What is claimed is:
 1. A communication apparatus, comprising: a protocolprocessing unit configured to send and receive link information on alink in a network having a redundant configuration according to aprotocol, to build topology information of the network from the linkinformation, and to set up a path in the network based on the topologyinformation; wherein the protocol processing unit includes a linkinformation advertising unit configured to advertise the linkinformation including information used to set up the path, saidinformation used to set up the path including reservable bandwidthinformation for each of a plurality of line types of lines provided bythe link with respect to each of a plurality of protection types of thelink; a topology information storing unit configured to store thetopology information; and a link information receiving unit configuredto receive the link information and to store the received linkinformation in the topology information storing unit, wherein saidinformation used to set up the path further includes channelavailability information indicating availability with respect to each ofa plurality of channels of the lines, wherein the protocol is a routingprotocol for GMPLS; the link information advertising unit is configuredto use a frame defined in the routing protocol and containing sub-framesto advertise the link information; and the link information advertisingunit is configured to use a protection type sub-frame to advertise eachof the protection types of the link, a reservable bandwidth sub-frame toadvertise the reservable bandwidth information for each of the linetypes with respect to each of the protection types of the link, and anadministrative group sub-frame to advertise the channel availabilityinformation, wherein the link information advertising unit is configuredto place mandatory sub-frames required by the routing protocol in theframe, to place the sub-frames used to advertise the protection types,the reservable bandwidth information for each of the line types withrespect to each of the protection types of the link, and the channelavailability information after the mandatory sub-frames, and to placethe administrative group sub-frame, the protection type sub-frame, andthe reservable bandwidth sub-frame that are the same as those includedin the mandatory sub-frames again after the sub-frames used for theadvertisement.
 2. The communication apparatus as claimed in claim 1,wherein the link information advertising unit is configured to useanother administrative group sub-frame as a marker indicating that theprotection type sub-frame and the reservable bandwidth sub-frame are tofollow.
 3. The communication apparatus as claimed in claim 1, whereinthe redundant configuration is implemented by a BLSR of SDH or SONET. 4.The communication apparatus as claimed in claim 1, wherein the channelavailability information comprises a bitmap indicating, with respect toeach of the channels, whether the channel is available or occupied.
 5. Acommunication apparatus, comprising: a protocol processing unitconfigured to send and receive link information on a link in a networkhaving a redundant configuration according to a protocol, to buildtopology information of the network from the link information, and toset up a path in the network based on the topology information; whereinthe protocol processing unit includes a link information advertisingunit configured to advertise the link information including informationused to set up the path, said information used to set up the pathincluding reservable bandwidth information for each of a plurality ofline types of lines provided by the link with respect to each of aplurality of protection types of the link; a topology informationstoring unit configured to store the topology information; and a linkinformation receiving unit configured to receive the link informationand to store the received link information in the topology informationstoring unit, wherein said information used to set up the path furtherincludes channel availability information indicating availability withrespect to each of a plurality of channels of the lines, wherein theprotocol is a routing protocol for GMPLS; the link informationadvertising unit is configured to use a frame defined in the routingprotocol and containing sub-frames to advertise the link information;and the link information advertising unit is configured to use anadministrative group sub-frame to advertise the channel availabilityinformation and the reservable bandwidth information for each of theline types with respect to each of the protection types of the link,wherein the link information advertising unit is configured to placemandatory sub-frames required by the routing protocol in the frame, toplace the sub-frame used to advertise the channel availabilityinformation and the reservable bandwidth information for each of theline types with respect to each of the protection types of the linkafter the mandatory sub-frames, and to place the administrative groupsub-frame that is the same as that included in the mandatory sub-framesagain after the sub-frame used for the advertisement.
 6. Thecommunication apparatus as claimed in claim 5, wherein the redundantconfiguration is implemented by a BLSR of SDH or SONET.
 7. Thecommunication apparatus as claimed in claim 5, wherein the channelavailability information comprises a bitmap indicating, with respect toeach of the channels, whether the channel is available or occupied.
 8. Amethod of sending and receiving link information on a link in a networkhaving a redundant configuration according to a protocol, where the linkinformation is used to build topology information of the network and thetopology information is used to set up a path in the network, the methodcomprising: advertising, by a processor, the link information includinginformation used to set up the path, said information used to set up thepath including reservable bandwidth information for each of a pluralityof line types of lines provided by the link with respect to each of aplurality of protection types of the link; and receiving, by theprocessor, the link information and storing the received linkinformation in a database to build the topology information, whereinsaid information used to set up the path further includes channelavailability information indicating availability with respect to each ofa plurality of channels of the lines, wherein the protocol is a routingprotocol for GMPLS; and said advertising the link information includesusing a frame defined in the routing protocol and containing sub-framesto advertise the link information; using a protection type sub-frame toadvertise each of the protection types of the link; using a reservablebandwidth sub-frame to advertise the reservable bandwidth informationfor each of the line types with respect to each of the protection typesof the link; and using an administrative group sub-frame to advertisethe channel availability information, wherein said advertising the linkinformation includes placing mandatory sub-frames required by therouting protocol in the frame; placing the sub-frames used to advertisethe protection types, the reservable bandwidth information for each ofthe line types with respect to each of the protection types of the link,and the channel availability information after the mandatory sub-frames;and placing the administrative group sub-frame, the protection typesub-frame, and the reservable bandwidth sub-frame that are the same asthose included in the mandatory sub-frames again after the sub-framesused for the advertisement.
 9. The method as claimed in claim 8, whereinsaid advertising the link information includes using anotheradministrative group sub-frame as a marker indicating that theprotection type sub-frame and the reservable bandwidth sub-frame are tofollow.
 10. The method as claimed in claim 8, wherein the redundantconfiguration is implemented by a BLSR of SDH or SONET.
 11. The methodas claimed in claim 8, wherein the channel availability informationcomprises a bitmap indicating, with respect to each of the channels,whether the channel is available or occupied.
 12. A method of sendingand receiving link information on a link in a network having a redundantconfiguration according to a protocol, where the link information isused to build topology information of the network and the topologyinformation is used to set up a path in the network, the methodcomprising: advertising, by a processor, the link information includinginformation used to set up the path, said information used to set up thepath including reservable bandwidth information for each of a pluralityof line types of lines provided by the link with respect to each of aplurality of protection types of the link; and receiving, by theprocessor, the link information and storing the received linkinformation in a database to build the topology information, whereinsaid information used to set up the path further includes channelavailability information indicating availability with respect to each ofa plurality of channels of the lines, wherein the protocol is a routingprotocol for GMPLS; and said advertising the link information includesusing a frame defined in the routing protocol and containing sub-framesto advertise the link information; and using an administrative groupsub-frame to advertise the channel availability information and thereservable bandwidth information for each of the line types with respectto each of the protection types of the link, wherein said advertisingthe link information includes placing mandatory sub-frames required bythe routing protocol in the frame; placing the sub-frame used toadvertise the channel availability information and the reservablebandwidth information for each of the line types with respect to each ofthe protection types of the link after the mandatory sub-frames; andplacing the administrative group sub-frame that is the same as thatincluded in the mandatory sub-frames again after the sub-frame used forthe advertisement.
 13. The method as claimed in claim 12, wherein theredundant configuration is implemented by a BLSR of SDH or SONET. 14.The method as claimed in claim 12, wherein the channel availabilityinformation comprises a bitmap indicating, with respect to each of thechannels, whether the channel is available or occupied.